Refactors the repository to more heavily and properly rely on Kustomize over Helm where possible. In doing so, this enables switching to the Gateway API over Ingress resources that are typically baked into Helm charts.

Major changes

• Replaces argo-cd Helm chart with the HA Kustomization from the official repository
• Replaces kube-prometheus-stack Helm chart with official Kustomization from prometheus-operator
• Removes ingress-nginx and replaces functionality with Gateway API support in Cilium

Minor changes

• Reclassify existing "apps" managed in this repository as "platform" or "system" ("apps" will be used later for user-facing workloads)
• Manage all apps (Argo CD) through a single ApplicationSet resource
• Removes the need to specify --load-restrictor LoadRestrictionsNone with Kustomize as Kustomizations no longer reference multiple paths for Helm values
• Prometheus now properly exposes resources metrics through the Metrics API for use by autoscaling
• The cert-manger chart now generates a ServiceMonitor resource to be scraped by Prometheus
• Now installs the Piraeus operator and creates a Linstor cluster in the local dev environment (requires the drbd9 kernel module on the host to not crash loop)
• Reduces the LimitNOFILE of Kind's containerd from infinity to 65535 to fix a runaway resource issue with the HAProxy component of Argo CD

Other notes

As a standard, Helm charts (where used) will now be inflated from a single values file in the base Kustomization and overlaid with standard Kustomize patching capabilities. However, Cilium continues to be managed with values per environment due to the level of difference between the environments.